Light emitting devices for light emitting diodes (LEDs)

ABSTRACT

Light emitting devices for light emitting diodes (LEDs) are disclosed. In one embodiment a light emitting device can include a substrate and a plurality of light emitting diodes (LEDs) disposed over the substrate in patterned arrays. The arrays can include one or more patterns of LEDs. A light emitting device can further include a retention material disposed about the array of LEDs. In one aspect, the retention material can be dispensed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/104,558 filed May 10, 2011, which relates to andclaims priority to U.S. Provisional Patent Application Ser. No.61/416,184, filed Nov. 22, 2010, and is a continuation-in-part of andclaims priority to each of U.S. Design patent application Ser. No.29/379,636, filed Nov. 22, 2010 and U.S. patent application Ser. No.13/028,972, filed Feb. 16, 2011. The disclosures of each of these priorapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to light emittingdevices and methods. More particularly, the subject matter disclosedherein relates to light emitting devices and methods comprising at leastone pattern and/or array of light emitting diodes (LEDs).

BACKGROUND

Light emitting devices, such as light emitting diodes (LEDs), may beutilized in packages for providing white light (e.g., perceived as beingwhite or near-white), and are developing as replacements forincandescent, fluorescent, and metal halide high-intensity discharge(HID) light products. A representative example of an LED devicecomprises a device having at least one LED chip, a portion of which canbe coated with a phosphor such as, for example, yttrium aluminum garnet(YAG). The phosphor coating can convert light emitted from one or moreLED chips into white light. For example, LED chips can emit light havingdesired wavelengths, and phosphor can in turn emit yellow fluorescencewith a peak wavelength of about 550 nm, for example. A viewer perceivesthe mixture of light emissions as white light. As an alternative tophosphor converted white light, light emitting devices of red, green,and blue (RGB) wavelengths can be combined in one device or package ordevice to produce light that is perceived as white.

Despite availability of various LED devices and methods in themarketplace, a need remains for improved devices and improvedmanufacturability of devices suitable for industrial and commerciallighting products and replacement of conventional light sources, such asfor example, 50 to 100 watt HID and high wattage compact fluorescent(CFL) lamps, outdoor lighting products, home luminaires, and retrofitlight bulbs. A need remains for improved devices suitable for a range oflow to high voltage applications. LED devices and methods describedherein can advantageously enhance light output performance andaccommodate various low to high voltage applications while promotingease of manufacture.

SUMMARY

In accordance with this disclosure, novel light emitting devices andmethods are provided that are well suited for a variety of applications,including industrial and commercial lighting products. It is, therefore,an object of the present disclosure herein to provide light emittingdevices and methods comprising at least one pattern, arrangement, and/orarray of light emitting devices optimized to enhance light outputperformance and accommodate various low to high voltage applicationswhile providing energy savings.

These and other objects of the present disclosure as can become apparentfrom the disclosure herein are achieved, at least in whole or in part,by the subject matter disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present subject matter includingthe best mode thereof to one of ordinary skill in the art is set forthmore particularly in the remainder of the specification, includingreference to the accompanying figures, in which:

FIG. 1 illustrates a top perspective view of an embodiment of a lightemitting device according to the disclosure herein;

FIG. 2 illustrates a side view of an embodiment of a light emittingdevice according to the disclosure herein;

FIGS. 3A and 3B illustrate top views of an embodiment of a lightemitting device having one or more patterns of light emitting diodes(LEDs) according to the disclosure herein;

FIG. 4 illustrates a top perspective view of an embodiment of a lightemitting device having one or more patterns of LEDs according to thedisclosure herein;

FIG. 5 illustrates a top view of an embodiment of a light emittingdevice according to the disclosure herein;

FIG. 6 illustrates a first cross-sectional view of a light emission areaof a light emitting device according to the disclosure herein;

FIG. 7 illustrates a second cross-sectional view of a light emissionarea of a light emitting device according to the disclosure herein;

FIG. 8 illustrates a top view of a light emitting device according tothe disclosure herein;

FIG. 9 illustrates a cross-sectional view of a gap area of a lightemitting device according to the disclosure herein;

FIG. 10 illustrates a top view of a light emitting device according tothe disclosure herein;

FIGS. 11 to 14B illustrate top views of embodiments of a light emittingdevice having one or more patterns of LEDs according to the disclosureherein; and

FIGS. 15A and 15B illustrate die attach used for LED devices accordingto the disclosure herein.

DETAILED DESCRIPTION

Reference will now be made in detail to possible aspects or embodimentsof the subject matter herein, one or more examples of which are shown inthe figures. Each example is provided to explain the subject matter andnot as a limitation. In fact, features illustrated or described as partof one embodiment can be used in another embodiment to yield still afurther embodiment. It is intended that the subject matter disclosed andenvisioned herein covers such modifications and variations.

As illustrated in the various figures, some sizes of structures orportions are exaggerated relative to other structures or portions forillustrative purposes and, thus, are provided to illustrate the generalstructures of the present subject matter. Furthermore, various aspectsof the present subject matter are described with reference to astructure or a portion being formed on other structures, portions, orboth. As will be appreciated by those of skill in the art, references toa structure being formed “on” or “above” another structure or portioncontemplates that additional structure, portion, or both may intervene.References to a structure or a portion being formed “on” anotherstructure or portion without an intervening structure or portion aredescribed herein as being formed “directly on” the structure or portion.Similarly, it will be understood that when an element is referred to asbeing “connected”, “attached”, or “coupled” to another element, it canbe directly connected, attached, or coupled to the other element, orintervening elements may be present. In contrast, when an element isreferred to as being “directly connected”, “directly attached”, or“directly coupled” to another element, no intervening elements arepresent.

Furthermore, relative terms such as “on”, “above”, “upper”, “top”,“lower”, or “bottom” are used herein to describe one structure's orportion's relationship to another structure or portion as illustrated inthe figures. It will be understood that relative terms such as “on”,“above”, “upper”, “top”, “lower” or “bottom” are intended to encompassdifferent orientations of the device in addition to the orientationdepicted in the figures. For example, if the device in the figures isturned over, structure or portion described as “above” other structuresor portions would now be oriented “below” the other structures orportions. Likewise, if devices in the figures are rotated along an axis,structure or portion described as “above”, other structures or portionswould now be oriented “next to” or “left of” the other structures orportions. Like numbers refer to like elements throughout.

Light emitting devices according to embodiments described herein maycomprise group III-V nitride (e.g., gallium nitride) based lightemitting diodes (LEDs) or lasers fabricated on a growth substrate, forexample, silicon carbide substrate, such as those devices manufacturedand sold by Cree, Inc. of Durham, N.C. For example, Silicon carbide(SiC) substrates/layers discussed herein may be 4H polytype siliconcarbide substrates/layers. Other silicon carbide candidate polytypes,such as 3C, 6H, and 15R polytypes, however, may be used. Appropriate SiCsubstrates are available from Cree, Inc., of Durham, N.C., the assigneeof the present subject matter, and the methods for producing suchsubstrates are set forth in the scientific literature as well as in anumber of commonly assigned U.S. patents, including but not limited toU.S. Pat. No. Re. 34,861; U.S. Pat. No. 4,946,547; and U.S. Pat. No.5,200,022, the disclosures of which are incorporated by reference hereinin their entireties.

As used herein, the term “Group III nitride” refers to thosesemiconducting compounds formed between nitrogen and one or moreelements in Group III of the periodic table, usually aluminum (Al),gallium (Ga), and indium (In). The term also refers to binary, ternary,and quaternary compounds such as GaN, AlGaN and AlInGaN. The Group IIIelements can combine with nitrogen to form binary (e.g., GaN), ternary(e.g., AlGaN), and quaternary (e.g., AlInGaN) compounds. These compoundsmay have empirical formulas in which one mole of nitrogen is combinedwith a total of one mole of the Group III elements. Accordingly,formulas such as AlxGa1−xN where 1>x>0 are often used to describe thesecompounds. Techniques for epitaxial growth of Group III nitrides havebecome reasonably well developed and reported in the appropriatescientific literature.

Although various embodiments of LEDs disclosed herein comprise a growthsubstrate, it will be understood by those skilled in the art that thecrystalline epitaxial growth substrate on which the epitaxial layerscomprising an LED are grown may be removed, and the freestandingepitaxial layers may be mounted on a substitute carrier substrate orsubmount which may have better thermal, electrical, structural and/oroptical characteristics than the original substrate. The subject matterdescribed herein is not limited to structures having crystallineepitaxial growth substrates and may be used in connection withstructures in which the epitaxial layers have been removed from theiroriginal growth substrates and bonded to substitute carrier substrates.

Group III nitride based LEDs according to some embodiments of thepresent subject matter, for example, may be fabricated on growthsubstrates (such as a silicon carbide substrates) to provide horizontaldevices (with both electrical contacts on a same side of the LED) orvertical devices (with electrical contacts on opposite sides of theLED). Moreover, the growth substrate may be maintained on the LED afterfabrication or removed (e.g., by etching, grinding, polishing, etc.).The growth substrate may be removed, for example, to reduce a thicknessof the resulting LED and/or to reduce a forward voltage through avertical LED. A horizontal device (with or without the growthsubstrate), for example, may be flip chip bonded (e.g., using solder) toa carrier substrate or printed circuit board (PCB), or wire bonded. Avertical device (without or without the growth substrate) may have afirst terminal solder bonded to a carrier substrate, mounting pad, orPCB and a second terminal wire bonded to the carrier substrate,electrical element, or PCB. Examples of vertical and horizontal LED chipstructures are discussed by way of example in U.S. Publication No.2008/0258130 to Bergmann et al. and in U.S. Publication No. 2006/0186418to Edmond et al., the disclosures of which are hereby incorporated byreference herein in their entireties.

An LED can be coated, at least partially, with one or more phosphorswith the phosphors absorbing at least a portion of the LED light andemitting a different wavelength of light such that the LED emits acombination of light from the LED and the phosphor. In one embodiment,the LED emits a white light combination of LED and phosphor light. AnLED can be coated and fabricated using many different methods, with onesuitable method being described in U.S. patent application Ser. Nos.11/656,759 and 11/899,790, both entitled “Wafer Level Phosphor CoatingMethod and Devices Fabricated Utilizing Method”, and both of which areincorporated herein by reference. In the alternative, LEDs can be coatedusing other methods such an electrophoretic deposition (EPD), with asuitable EPD method described in U.S. patent application Ser. No.11/473,089 entitled “Close Loop Electrophoretic Deposition ofSemiconductor Devices”, which is also incorporated herein by reference.It is understood that LED devices and methods according to the presentsubject matter can also have multiple LEDs of different colors, one ormore of which may be white emitting.

Referring now to FIGS. 1 to 15B, FIG. 1 illustrates a top view of alight emitting or LED device, generally designated 10. LED device 10 cancomprise a substrate 12 over which an emission area, generallydesignated 16, can be disposed. In one aspect, emission area 16 can bedisposed substantially centrally with respect to LED device 10. In thealternative, emission area 16 can be disposed in any location over LEDdevice 10, for example, in a corner or adjacent an edge. In one aspect,emission area 16 can comprise a substantially circular shape. In otheraspects, emission area 16 can comprise any other suitable shape, forexample, a substantially square, oval, or rectangle shape. LED device 10can comprise a single emission area 16 or more than one emission area16. Notably, LED device 10 can comprise a uniform optical source in theform of emission area which can simplify the manufacturing process formanufacturers of light products requiring a single component. LED device10 can further comprise a retention material 14 disposed at leastpartially about emission area 16 where retention material 14 can bereferred to as a dam. Retention material 14 can also be disposed over atleast one electrostatic discharge (ESD) protection device, such as aZener diode 44 (FIG. 9). In some aspects, retention material can bedisposed over two Zener diodes 44 connected in series between twoelectrical elements (FIG. 8).

Substrate 12 can comprise any suitable mounting substrate, for example,a printed circuit board (PCB), a metal core printed circuit board(MCPCB), an external circuit, or any other suitable substrate over whichlighting devices such as LEDs may mount and/or attach. Emission area 16can be in electrical and/or thermal communication with substrate 12. Oneor more intervening layers can be disposed between emission area 16 andsubstrate 12 such that emission area 16 is indirectly disposed oversubstrate 12 thereby indirectly electrically and/or thermallycommunicating with substrate 12. In the alternative, emission area 16can directly mount over substrate 12 thereby directly electricallyand/or thermally communicating, or connecting, with substrate 12. In oneaspect and for example only without limitation, substrate 12 cancomprise a compact dimension of 22 millimeter (mm)×22-mm squarefootprint. In other aspects, substrate 12 can comprise any suitabledimension and/or shape, for example, a circular or rectangular shape.

Emission area 16 can comprise a plurality of LED chips, or LEDs 25disposed within and/or below a filling material 40 such as illustratedin FIG. 7. LEDs 25 can comprise any suitable size and/or shape. Forexample, LEDs 25 can have a rectangle, square, or any other suitableshape. In one aspect, filling material 40 can comprise an encapsulanthaving a predetermined, or selective, amount of phosphors and/orlumiphors in an amount suitable for any desired light emission, forexample, suitable for white light conversion. Filling material 40 caninteract with light emitted from the plurality of LEDs 25 such that aperceived white light, or any suitable and/or desirable wavelength oflight, can be observed. Any suitable combination of encapsulant and/orphosphors can be used, and combinations of different phosphors forresulting in desired light emission can be used. In other aspects,filling material 40 can comprise a molded lens material. Fillingmaterial 40 can be substantially opaque such that emission area 16 canbe substantially opaque (as illustrated in FIG. 1), transparent, orsemi-transparent depending upon, for example, the amount and type ofphosphor used. Retention material 14 can be adapted for dispensing, orplacing, about at least a portion of emission area 16. After placementof retention material 14, filling material 40 can be selectively filledto any suitable level within the space disposed between one or moreinner walls of retention material 14. For example, filling material 40can be filled to a level equal to the height of retention material 14 orto any level above or below retention material. The level of fillingmaterial 40 can be planar or curved in any suitable manner, such asconcave or convex.

Still referring to FIG. 1, LED device 10 can also comprise at least oneopening or hole, generally designated 20, that can be disposed throughor at least partially through substrate 12 for facilitating attachmentof LED device 10 to an external substrate or surface. For example, oneor more screws can be inserted through the at least one hole 20 forsecuring device 10 to another member, structure, or substrate. LEDdevice 10 can also comprise one or more electrical attachment surfaces18. In one aspect, attachment surfaces 18 comprise electrical contactssuch as solder contacts. Attachment surfaces 18 can be any suitableconfiguration, size, shape and/or location and can comprise positive andnegative electrode terminals through which an electrical current orsignal can pass when connected to an external power source. One or moreconducting wires (not shown) can be attached and electrically connectedto attachment surfaces 18 when welded, soldered, or any other suitableattachment method known. Electrical current or signal can pass into LEDdevice 10 from the external wires electrically connected to theattachment surfaces 18 and into the emission area 16 to facilitate lightoutput. Attachment surfaces 18 can electrically communicate withemission area 16 which comprises one or more LEDs 25. Attachmentsurfaces 18 can electrically communicate with first and secondconductive traces 33 and 34 (see FIG. 8) and therefore LEDs 25 which maybe electrically connected using electrical connectors. Electricalconnectors can comprise wirebonds or other suitable members forelectrically connecting LEDs 25 to first and second conductive traces 34and 33.

LED device 10 can further comprise an indicator sign or symbol fordenoting the electrical polarity for a given a side of LED device 10.For example, a first symbol 22 can comprise a “+” sign denoting the sideof LED device 10 comprising the positive electrode terminal. A secondsymbol 23 can comprise a “−” sign denoting the side of LED device 10comprising the negative electrode terminal. One or more test points 15can be located adjacent either a positive or negative side of the devicefor testing the electrical and/or thermal properties of the LED device10. In one aspect, test point 15 can be disposed adjacent the negativeside, or terminal of LED device 10.

FIG. 2 illustrates a side view of LED device 10. As illustrated by FIGS.1 and 2, retention material 14 can comprise a substantially circular damdisposed about at least a portion of emission area 16 and disposed oversubstrate 12. Retention material 14 can be dispensed, positioned orotherwise placed over substrate 12 and can comprise any suitable sizeand/or shape. Retention material 14 can comprise any suitable reflectivematerial and can comprise a clear or opaque white material such as, forexample, a silicone or epoxy material. Filler particles such as titaniumdioxide (TiO₂), for example, can be used and added to retention material14 for providing an opaque material. Retention material 14 can bedispensed or deposited in place using an automated dispensing machinewhere any suitable size and/or shape of dam can be formed. In oneaspect, a circular shape as shown can be dispensed, although any otherconfiguration could also be provided such as, for example, a rectangularconfiguration, a curved configuration and/or any combination of desiredconfigurations and cross-sectional shapes. As FIG. 2 illustrates in aside view of LED device 10, retention material 14 can comprise a roundedouter wall 24 such that the upper surface of retention material 14opposite substrate 12 is rounded. Rounding, or curving outer wall 24 ofretention material 14 may further improve the amount of light reflectedby LED device 10.

Retention material 14 can comprise any material known in the art, forexample, a silicone material comprising 7% fumed silica+3% TiO₂+methylsilicone. As illustrated in FIGS. 3A and 3B, retention material 14 canbe dispensed after wirebonding of the one or more LEDs 25 such thatretention material 14 is disposed over and at least partially coverswirebonds 26 to contain at least a portion, such as one end of each ofwirebonds 26 within retention material 14. In FIGS. 3A and 3B, wirebonds26 for the first and last, or outermost edge LEDs 25A for a given set ofLEDs such as LEDs 25 are disposed within retention material 14. In oneaspect, retention material 14 can be “planed” during dispersion at roomtemperature for accurate volume and/or height control. The addition ofTiO₂ can increase reflection about the emission area 16 to further tooptimize light emission of LED device 10. Fumed silica can be added as athixotropic agent. Dispersing retention material 14 can allow increasedboard space and the ability to withstand higher voltages. In someaspects, LED device 10 can be operable at 42 volts (V) or higher.

FIGS. 3A, 3B and 4 illustrate emission area 16 without a layer offilling material 40. FIGS. 3A and 3B illustrate LED device 10 andemission area 16 comprising at least one pattern, or arrangement, ofLEDs. LEDs 25 can be arranged, disposed, or mounted over a conductingpad 30. LEDs 25 can be arranged or disposed in sets of LEDs, that cancomprise one or more strings or LEDs, and a given set of LEDs can forexample be one or more strings of LEDs electrically connected in seriesor any other suitable configuration. More than one set of LEDs can beprovided, and each set of LEDs can be arranged in parallel to one ormore other sets of LEDs. As described further herein, the LEDs in anygiven set or string of LEDs can be arranged in any suitable pattern orconfiguration, and even LEDs within a given set or string of LEDs can bearranged or disposed in one or more different patterns orconfigurations. For example, FIG. 3A illustrates at least three sets ofLEDs arranged in three patterns, for example, a first pattern P1, asecond pattern P2, and a third pattern P3. Each of patterns P1, P2, andP3 can comprise a consistent pattern design across emission area 16.More than one of patterns P1, P2, and/or P3 can be used. Each ofpatterns P1, P2, and/or P3 can alternate or be arranged in any suitableconfiguration. For illustration purposes, only three patterns areillustrated. Any number of patterns or arrangements is contemplated, andpatterns can comprise any suitable design, for example, a checkerboarddesign or a grid design or arrangement wherein the LEDs can be at leastsubstantially aligned in at least two directions. FIG. 3B illustrates atleast three sets of LEDs arranged in patterns, for example, a firstpattern P1A, second pattern P2, and a third pattern P3A which combineone or more of patterns P1, P2, and P3 illustrated in FIG. 3A. Forexample, patterns P1A and P3A can comprise a combination of more thanone pattern. In one aspect, pattern P1A can comprise a grid arrangementor pattern and a straight line arrangement or pattern. In one aspect,pattern P3A can comprise the checkerboard and straight line patterndesigns. Each of patterns P1A and P3A can comprise 14 LEDs 25, sevenLEDs of each pattern design. For illustration purposes, only twocombinations are illustrated. However, please note that each set of LEDscan comprise a combination of having more than two patterns.

Still referring to FIGS. 3A and 3B, conducting pad 30 can beelectrically and/or thermally conducting and can comprise any suitableelectrically and/or thermally conducting material. In one aspect,conducting pad 30 can comprise a conductive metal. In one aspect shownin FIG. 3A, emission area 16 can comprise one or more LEDs 25 arrangedin a single pattern over conducting surface, or pad 30. In analternative, LEDs can be provided that are a combination of more thanone pattern of LEDs, such as LEDs 25, arranged over conducting pad 30 asFIG. 3B illustrates. As noted above, emission area 16 can comprise acombination of different arrangements or patterns, for example, acombination of first pattern P1, second pattern P2 and/or third patternP3 for optimizing light emission and device brightness. Each set, orstring of LEDs 25 disposed over conducting pad 30 can comprise outermostLEDs 25A with one or more LEDs 25 disposed therebetween. Each string ofLEDs 25 can comprise the same or a different pattern, for example,patterns P1, P2, and/or P3. Strings of LEDs 25 can comprise diodes ofthe same and/or different colors, or wavelength bins, and differentcolors of phosphors can be used in the filling material 40 (FIG. 7)disposed over LEDS 25 that are the same or different colors in order toachieve emitted light of a desired wavelength. The one or more patternsof LEDs 25 can comprise an array of LEDs within emission area 16.

FIGS. 3A, 3B, and 4 illustrate emission area 16 comprising, for example,10 lines, or strings, of LEDs 25. Each string of LEDs 25 can compriseany suitable number of LEDs electrically connected between outermostLEDs 25A which can connect to respective electrical elements. In oneaspect, each string of LEDs 25 can comprise at least 14 LEDs. In oneaspect, LED device can comprise at least 140 LEDs arranged in an array.The arrangements, patterns, and/or combination of multiple patternsherein can comprise an array for optimizing color uniformity andbrightness of light emitted from LED device 10. The LEDs can beelectrically connected in series using one or more wirebonds 26 forattaching bond pads of adjacent LEDs 25. In one aspect as shown in FIG.3A, first pattern P1 can comprise the first and tenth strings of 14 LEDs25. First pattern P1 can comprise two opposing lines of LEDs 25 disposedbetween the first and last, or outermost LEDs 25A of the series. In oneaspect, first pattern P1 comprises what is referred to herein as a gridarrangement, pattern or design, where at least two LEDs are at leastsubstantially aligned in at least two directions and can include single,unaligned LEDs at opposing ends of a set or string of LEDs. Each of theLEDs 25 comprising first pattern P1 can be electrically connected inseries. In one aspect, second arrangement or second pattern P2 can bedisposed adjacent first pattern P1, for example, located at the secondand ninth strings of LEDs 25. In one aspect, second pattern P2 cancomprise 14 total LEDs 25 wherein each of the 14 LEDs 25 can be arrangedadjacent each other along a horizontal line in a straight line design,or arrangement, and each of the 14 LEDs 25 can be electrically connectedin series. Any suitable number of LEDs 25 can be connected in anysuitable configuration or arrangement such as in series to form a stringhaving a suitable pattern. Care must be taken when connecting LEDs 25 inseries such that the positive or negative electrode of a preceding LEDelectrically connects to an electrode of opposite electrical polarityfor a subsequent LED for allowing electrical current to flow properlythrough the string of LEDs 25.

Third pattern P3 shown in FIG. 3A can comprise a checkerboard patternhaving a checkerboard design, or arrangement of LEDs 25 electricallyconnected in series. In one aspect, at least 14 LEDs 25 can comprise thecheckerboard pattern, and third pattern P3 can be disposed betweenand/or alternate with strings of LEDs having second pattern P2. Thecheckerboard pattern or third pattern P3 can comprise a set of LEDs 25alternating both above and below a horizontal line. Patterns P1, P2, andP3 are not limited in the shape of pattern or to at least 14 LEDs, butrather, patterns can comprise any suitable arrangement and any suitablenumber of LEDs 25. For illustration purposes, only three patterns areshown although any suitable number of patterns could be utilized. Thealternating LEDs 25 of third pattern P3 can optimize light output byensuring uniform coverage and spatial alignment over conducting pad 30such that light emission is uniform and improved. Third pattern P3 canrepeat from the third through the eighth string of LEDs 25. First andlast LEDs 25A in a given string of LEDs 25 for each of patterns P1, P2,and/or P3 can electrically connect to first and second conductive traces33 and 34 (see FIGS. 7, 8) for receiving and transmitting electricalcurrent or signal through and illuminating a given string of LEDs 25.

The LEDs even in a single set or string in emission area 16 can compriseLEDs in more than one pattern or configuration. For example, FIG. 3Billustrates one aspect of a possible arrangement of LEDs in emissionarea 16 where there are at least two sets, shown here as strings withoutlimitation, of LEDs 25 and where LEDs 25 for some sets or strings arearranged in different patterns or configurations with respect to anotherset or string of LEDs and even within one single set or string of LEDs.Any two given separate sets or strings of LEDs 25 can be electricallyconnected in a pattern such that some or all of the LEDs within each ofthe two sets or strings of LEDs can be arranged in different patterns,in identical patterns, or in any combination of patterns. In otherwords, the LEDs in any given set or string can be disposed in differentor identical patterns with respect not only to the LEDs in that set orstring but can also be disposed in any pattern with respect to anotherset or string of LEDs and the two sets or strings can in one aspect beparallel to one another. For example, LEDs 25 in FIG. 3B can be disposedin one aspect such that emission area 16 comprises a combination ofdifferent arrangements or patterns, for example, a first pattern P1A, asecond pattern P2 A and/or a third pattern P3A for optimizing lightemission and device brightness. As noted earlier, patterns P1A and P3Aillustrate a combination of two different patterns, for example at leasttwo of the checkerboard, straight line and/or grid arrangement, however,combinations of more than two patterns is hereby contemplated. Onlythree pattern arrangements have been disclosed (i.e., checkerboard,grid, straight line), but any suitable arrangement or pattern design canbe used. Each string of LEDs 25 disposed over conducting pad 30 cancomprise outermost LEDs 25A with one or more LEDs 25 disposedtherebetween. Each set or string of LEDs 25 can comprise the same or adifferent pattern, for example, patterns P1A, P2A, and/or P3A. Sets orstrings of LEDs 25 can comprise diodes of the same and/or differentcolors, or wavelength bins, and different colors of phosphors can beused in the filling material 40 (FIG. 7) disposed over LEDS 25 that arethe same or different colors in order to achieve emitted light of adesired wavelength. The one or more patterns of LEDs 25 can comprise anarray of LEDs within emission area 16. As FIG. 3B illustrates, forexample, in pattern P3A, sets of LEDS 25 can comprise rectangular LEDsarranged where the major (i.e., long) axis of a first LED is disposed ina different orientation than the major axis of at least a second LED.That is, a given set of LEDs 25 can comprise LEDs 25 in differentorientations. In other aspects, as illustrated in FIG. 3A for example,pattern P2 and pattern P3 can comprise sets of rectangular LEDs 25 wherethe major axis is the same is the same for the given set but differentfrom the orientation of other sets.

The various LED arrangements and device designs as described herein areadvantageous for providing a light emitting device with excellentperformance and output while still being a small light emitting devicewhere pressure exists to provide small devices while maintaining qualityperformance and light output.

FIG. 5 illustrates a second embodiment of an LED device, generallydesignated 50 which is similar in form and function to LED device 10.LED device 50 can comprise substrate 12 and emission area 16 disposedover substrate 12. Emission area 16 can comprise any suitable size,shape, number and/or be disposed at any suitable location over substrate12. Retention material 14 can be disposed over substrate 12 and at leastpartially about emission area 16. LED device 50 can comprise one or moreopenings or holes 20, disposed through substrate 12 for facilitatingattachment of LED device 10 to an external substrate or surface. LEDdevice 50 can comprise first and second symbols 22 and 23 for denotingthe electrical polarity of LED device 50. LED device 50 illustrates testpoint 15 disposed adjacent the positive or side of the device fortesting the electrical and/or thermal properties of the LED device 50.LED device 50 further can comprise at least one electrical attachmentsurface 18 that can electrically connect to one or more external wires(not shown) for facilitating the flow of electric current into emissionarea 16 of LED device 50. In one aspect, attachment surface 18 cancomprise a shape having curved corners. Rounding the corners, or edgesof attachment surfaces 18 may better contain the flow of solder over thedevice than sharp corners when attaching one or more external conductivewires (not shown) to LED device 50.

FIG. 6 illustrates a portion of a cross-section along an edge ofconducting pad 30 of FIGS. 3A and 3B wherein the emission area 16 hasnot been filled with filling material 40 such as encapsulant and/orphosphors. FIG. 6 illustrates LEDs 25 comprising an outermost LED 25Aand adjacent LED for a given string of LEDs within emission area 16.FIG. 7 illustrates a portion of a cross-section of FIG. 1 whereinfilling material 40 is disposed over emission area 16. For illustrationpurposes, four LEDs 25 are illustrated and electrically connected inseries in FIG. 7. However, as noted earlier, each string, or pattern ofLEDs 25 can comprise any suitable number of LEDs 25. In one aspect, eachstring of LEDs can comprise 14 LEDs 25. FIGS. 6 and 7 illustrate one ormore LEDs 25 connected in series by one or more wirebonds 26. LEDs 25can be arranged over conducting pad 30 and can thermally communicatedirectly with conducting pad 30 or indirectly through one or moreintervening layers. LEDs 25 can attach to conducting pad 30 orintervening layers using any attachment means known in art. In oneaspect, LEDs 25 can attach using solder pastes, epoxies, or flux.Conducting pad 30 can be formed integral as one piece of substrate 12 orcan comprise a separate layer disposed over substrate 12. Conducting pad30 can dissipate heat generated by the one or more LEDs 25.

As FIGS. 6 and 7 further illustrate, the outermost LEDs 25A for aseries, string, or pattern of LEDs 25 can electrically communicate orconnect to one or more electrical elements. Electrical elements cancomprise first and second conductive traces 33 and 34 configured toflow, or supply electrical signal or current to the respective stringsof LEDs 25. One of first and second conductive traces 33 and 34 cancomprise an anode and the other a cathode. The electrical polarity canbe denoted by first and second symbols 22 and 23 (FIG. 1) as discussedearlier. Conducting pad 30 and conductive traces 33 and 34 can compriseany suitable electrical and thermally conductive materials and cancomprise either the same or different materials. In one aspect,conducting pad 30 and conductive traces can comprise a layer of copper(Cu) deposited over substrate using any suitable technique. Anelectrically insulating solder mask 32 can be disposed at leastpartially between conducting pad 30 and respective conductive traces 33and 34 such that when solder is used to attach one or more LEDs 25 overconducting pad 30, the solder cannot electrically connect with theconductive traces 33 and 34 thereby causing one or more strings of LEDs25 to become electrically shorted.

FIG. 6 illustrates various placement areas, positions, or locations ofretention material 14 about emission area 16. In one aspect, retentionmaterial 14 can be dispensed about at least a portion, or entirely aboutemission area 16. Conventional devices can comprise a molded as opposedto dispensed dam placed at a location such as prior art location PAshown in broken lines in FIG. 6 and disposed along an edge of wheresolder mask 32 contacts first conductive trace 34. The present subjectmatter envisions retention material 14 disposed in areas, positions, orlocations R1, R2, and/or any location therebetween. When retentionmaterial 14 is disposed in locations R1 or R2, it can be disposed overand cover at least a portion of one or more wirebonds 26 connectingoutermost LEDs 25A to electrical elements, such as conductive trace 34.When in location R1, retention material 14 can be disposed at leastpartially over each of solder mask 32 and wirebond 26 connected tooutermost LED 25A for a respective string of LEDs 25. In one aspect,retention material 14 can be disposed entirely over the portion ofsolder mask 32 disposed between conducting pad 30 and conductive trace34 and/or entirely over wirebond 26 when in location R1. In anotheraspect, retention material 14 can be disposed over and at leastpartially or entirely cover each of the wirebonds 26 of each of theoutermost LEDs 25A for each string of LEDs 25 disposed in emission area16. The retention material can be dispensed in a predetermined locationon the substrate 12 for providing a suitable distance between theretention material 14 and the one or more LEDs 25. Notably, when inlocation R1, retention material 14 can eliminate the need for soldermask 32 as retention material would be disposed between conducting pad30 and first and/or second conductive traces 33, 34. Location R2illustrates retention material 14 disposed at least partially oversolder mask 32 and at least partially over wirebond 26 of outermost LED25A. As illustrated, retention material 14 according to the subjectmatter herein can comprise a substantially rounded or hemispheric shapedcross-section. Rounding retention material 14 can increase the surfacearea from which light may be emitted and/or reflected.

FIG. 7 illustrates a string of one or more LEDs 25, for illustrationpurposes four LEDs 25 are shown but strings of LEDs 25 can comprise anysuitable number of LEDs, for example, 14 LEDs 25 arranged in series.FIG. 7 illustrates a cross-section of substrate 12 over which LEDs 25can be mounted or otherwise arranged. Substrate 12 can comprise, forexample, conducting pad 30, first and second conductive traces 33 and34, and solder mask 32 at least partially disposed between conductingpad 30 and each of conductive traces 33 and/or 34. As noted earlier, ifretention material is positioned adjacent outermost LEDs 25A, forexample in location R1, solder mask 32 between conducting pad 30 andfirst and second conductive traces 33 and 34 can be eliminated as itwould no longer be necessary. Solder mask 32 can be disposed betweenconductive traces 33 and 34 and attachment surfaces 18 (FIG. 8), theproximal edges of which can be seen in FIG. 7 adjacent retentionmaterial 14, adjacent the outer wall 24 of retention material 14.Substrate 12 can further comprise a dielectric layer 36, and a corelayer 38. For illustration purposes, substrate 12 can comprise a MCPCB,for example, those available and manufactured by The Bergquist Companyof Chanhassan, Minn. Any suitable substrate 12 can be used, however.Core layer 38 can comprise a conductive metal layer, for example copperor aluminum. Dielectric layer 36 can comprise an electrically insulatingbut thermally conductive material to assist with heat dissipationthrough substrate 12. FIG. 7 illustrates retention material 14 arranged,for example, in position R2 at least partially over each of solder mask32 and the wirebond 26 connecting to conductive traces 33 and 34. FIG. 7illustrates filling material 40 disposed over the one or more LEDs 25.Filling material 40 can be selectively filled to any suitable levelhigher, lower, or equal to the height of retention material 14.Wirebonds 26 of the outermost LEDs 25A as shown can be at leastpartially disposed within retention material 14.

FIG. 7 further illustrates examples of first and second heights H1 andH2 of filling material 40 which can be selectively filled within LEDdevice 10. First height H1 can comprise a height at which fillingmaterial 40 is disposed over the LEDs 25. The height may vary due toprocess variability, so an average height above the string of LEDs 25can be used and controlled for optimal brightness. Second height H2 cancomprise a height at which filling material 40 is selectively disposedover a top surface of conducting pad 30. Second height H2 can becontrolled, for example, by controlling the location of retentionmaterial 14 and whether it assumes location R1, R2 or any positiontherebetween. Second height H2 can also be controlled by controlling theamount of filling material 40 dispensed into the cavity defined byretention material 14.

Controlling the volume of filling material 40 within the cavity, or damdefined by retention material 14 can affect first and second heights H1and/or H2 and can notably allow for fine-tuning, or micro-tuning thecolor, or wavelength, of light emitted from LED device 10. Micro-tuningthe color of LED devices 10 can therefore ideally increase productyields to 100%. For example, the amount of color affecting components,including but not limited to phosphors, contained in filling material 40can be selectively added and the first and/or second heights H1, H2 canbe selectively controlled by under or over filling the filling material40 within emission area 16 depending on the wavelength of LEDs 25 usedwithin device 10. Location of retention material 14, for example,locating retention material at R1, R2, or any position or distancetherebetween can also affect first and/or second heights H1 and H2.Micro-tuning color can be achieved over multiple devices or on a perdevice, or package, basis by changing, for example the ratio of volumeof phosphor to overall dispense capability volume of filling material40. The ratio of volume of phosphor to overall dispense capabilityvolume of filling material 40 can be adjusted based on the wavelengthbin of LEDs 25 selected for use in a given device to attain the desiredoverall wavelength output of LED device 10. By manipulating, forexample, the diameter of the dam provided by retention material 14and/or the height of retention material 14, each of which can affectheights H1 and/or H2 and therefore the volume of fill material, thecolor of individual devices 10 can be micro-tuned thereby attaininghigher process yields. Notably, selectively controlling a volume of thefill material such that color-affecting components of the fill materialcan be fine-tuned allows for light produced by the one or more LEDs tofall within a predetermined and precise color range.

FIG. 8 illustrates LED device 10 comprising substrate 12 prior toarranging, dispensing, or otherwise placing retention material 14 aboutat least a portion of emission area 16. For illustration purposes, onlya first string of LEDs 25 is illustrated, however, as noted earlier,emission area can comprise more than one strings of LEDs 25 electricallyconnected in series. In one aspect, LED device 10 comprises 10 stringsof LEDs 25 connected in series. As illustrated, prior to placingretention material 14, substrate 12 can comprise first and secondconductive traces 33 and 34 arranged in a substantially circulararrangement about conducting pad 30 such that LEDs arranged overconducting pad 30 can electrically communicate to each trace bywirebonding and wirebonds 26 or by any other suitable attachment method.As illustrated, outermost LEDs 25A for a respective string of LEDs 25can electrically connect to conductive traces.

At least one gap 42 can exist between conductive traces 33 and 34. LEDdevice 10 and devices disclosed herein can further comprise elements toprotect against damage from ESD positioned, or disposed in the gap 42.In one aspect, different elements can be used such as various verticalsilicon (Si) Zener diodes, different LEDs arranged reverse biased toLEDs 25, surface mount varistors and lateral Si diodes. In one aspect,at least one Zener diode 44 can be disposed between ends of first andsecond conductive traces 33 and 34 and reversed biased with respect tothe strings of LEDs 25. In one aspect, two Zener diodes 44 can beelectrically connected in series using one or more wirebonds 46 betweenfirst and second conductive traces 33 and 34 for higher voltageapplications. As Zener diodes 44 are typically black and absorb light,placing the at least one Zener diode 44 in gap 42 between conductivetraces 33 and 34 and also beneath retention material 14 can furtherimprove light output intensity.

FIG. 8 also illustrates one possible location for conducting pad 30.That is, conducting pad 30 can comprise a substantially centrallylocated circular pad disposed between conductive traces 33 and 34.Conducting pad 30 however, can be located at any suitable location oversubstrate and any location other than substantially center the device.Solder mask 32 can be disposed at least partially between respectiveconductive traces and conducting pad 30, such that the solder mask 32comprises a substantially circular arrangement about conducting pad 30.Solder mask 32 can also be disposed in areas outside of the conductivetraces, for example, between the respective conductive traces and one ormore attachment surfaces 18. Broken lines 52 illustrate one possibleaspect of the size and/or shape of conducting material comprising theconductive traces 33 and 34. The lines are broken to illustrate how thematerial can be disposed under solder mask 32. Thus, attachment surfaces18 electrically and/or thermally communicate with respective conductivetraces, and can comprise the same layer of material. External,conductive wires (not shown) can electrically connect to attachmentsurfaces 18, and electrical current or signal can flow from theattachment surfaces 18 to the respective conductive traces. Theelectrical current can flow along the conducting material designated bydotted lines 52 disposed below the layer of solder mask 32. Theelectrical current can flow into and/or out of the conductive traces andtherefore into and out of respective strings of LEDs 25 mounted overconducting pad 30.

As noted earlier, Zener diodes 44 are typically black and absorb light.FIG. 9 illustrates Zener diode 44 upon placement of the retentionmaterial. In one aspect, retention material 14 can be disposed at leastpartially over the at least one Zener diode 44. In another aspect,retention material 14 can be disposed entirely over the at least oneZener diode 44 such that the diode is completely covered for furtherimproving light output intensity. Zener diode 44 can be disposed over anelectrically and/or thermally conducting surface or area 54 such thatcurrent can flow through the diode 44, into the wirebonds 46, and torespective conductive traces 33 and 34.

LED devices disclosed herein can advantageously consume less energywhile delivering equal or greater illumination. In one aspect, when usedin traditional downlight applications, luminaires based on LED devices10 and/or 50 can deliver 38% more illumination than a 26-watt CFL or a100-watt incandescent bulb, while consuming only 14 watts. In oneaspect, LED device 10 can enable a 60-watt A-lamp equivalent whileconsuming only 11 watts. LED device 10 can comprise a light output of1050 lumens at 11 watts, or 2000 lumens at 27 watts, with a 3000-Kwarm-white color temperature.

FIG. 10 illustrates another embodiment of an LED device, generallydesignated 55. LED device 55 illustrates substrate 12 prior toarranging, dispensing, or otherwise placing retention material 14 (FIG.11) about at least a portion of emission area 16. For illustrationpurposes, only a first string of LEDs 25 is illustrated, however,emission area can comprise more than one string of LEDs 25 electricallyconnected in series. Each string of LEDs 25 can comprise the same or adifferent pattern. LED device 60 is similar in form and function to LEDdevice 10 previously described with respect to FIG. 8. For example,prior to placing retention material 14, substrate 12 can comprise firstand second conductive traces 33 and 34 arranged in a substantiallycircular arrangement about conducting pad 30 such that LEDs arrangedover conducting pad 30 can electrically communicate to each trace bywirebonding via wirebonds 26 or any other suitable attachment method. Asillustrated, outermost LEDs 25A for a respective string of LEDs 25 canelectrically connect to the conductive traces. In fact, for LED devicesdescribed herein, emission area 16 can comprise a single, undividedmounting area at least partially defined by outermost LEDs 25A, with theoutermost LEDs 25A being wirebonded via wirebonds 26 to contact areas,such as conductive traces 33 and 34. LEDs 25 that are not the outermostLEDs 25A are wirebonded via wirebonds 26 in strings having one or morepatterns or arrays.

At least one gap 42 can exist between conductive traces 33 and 34. Inthis embodiment, one or more ESD protection device or Zener diode 44 canbe disposed in gap 42 and can be electrically connected, or mounted toconductive area 54. In this embodiment, conductive area 54 can comprisean area larger than a footprint of Zener diode 44. Zener diode 44 can bepositioned over conductive area 54 between ends of first and secondconductive traces 33 and 34. Zener diode 44 can be reversed biased withrespect to the one or more strings of LEDs 25. For example, when oneZener diode 44 is used, one or more wirebonds 46 can connect conductivearea 54 to one of first and second conductive traces 33 and 34 such thatZener diode 44 can be reverse biased with respect to the strings of LEDs25. As Zener diodes 44 are typically black and absorb light, placing theat least one Zener diode 44 in gap 42 between conductive traces 33 and34 and also beneath retention material 14 (FIG. 9) can further improvelight output intensity.

FIG. 10 also illustrates one possible location for test point 15. Testpoint 15 can be disposed within the area marked by broken lines 52 whichcorrespond to conducting material disposed under solder mask. Brokenlines 52 illustrate one possible aspect of the size and/or shape of theconducting material which can be deposited on or in substrate 12 forelectrically coupling conductive traces 33 and 34 and attachmentsurfaces 18. The electrical coupling allows electrical current to becommunicated from attachment surfaces 18 to the one or more strings ofLEDs 25 electrically connected to traces 33 and 34. The lines are brokento illustrate how the material can be disposed under solder mask 32.Thus, test point 15 and attachment surfaces 18 electrically and/orthermally communicate with respective conductive traces, and cancomprise the same layer of material. Solder mask 32 can be deposited ordisposed at least partially between respective conductive traces andconducting pad 30, such that the solder mask 32 comprises asubstantially circular arrangement about conducting pad 30. Conductivepad 30 can comprise one or more marks or notches 62 for orientationpurposes and for proper alignment of retention material 14.

Solder mask 32 can also be deposited in areas outside of the conductivetraces, for example, between the respective conductive traces and one ormore attachment surfaces 18 and/or test point 15. External, conductivewires (not shown) can electrically connect to attachment surfaces 18,and electrical current or signal can flow from the attachment surfaces18 to the respective conductive traces. The electrical current can flowalong the conducting material designated by dotted lines 52 disposedbelow the layer of solder mask 32. The electrical current can flow intoand/or out of the conductive traces and therefore into and out ofrespective strings of LEDs 25 mounted over conducting pad 30. In oneaspect, test point 15 can allow electrical properties of the device tobe tested when probed with an electrically conductive test wire ordevice (not shown). The arrangement illustrated by FIG. 10, i.e., thelocation of conductive traces 33 and 34, conductive area 54, Zener diode44, and test point 15 prior to placing retention material 14 cancorrespond to any one of the previously described LED devices e.g., 10and 50 or any of the devices described in FIGS. 11-14. For example, LEDdevices described in FIG. 11-14 can comprise at least one opening orhole, generally designated 20, that can be disposed through or at leastpartially through substrate 12 for facilitating attachment of the LEDdevices to an external substrate or surface. In addition first symbol 22and second symbols can be used to denote the portions of the LED devicescomprising positive and negative electrode terminals. One or more testpoints 15 can be located adjacent either a positive or negative side ofthe device for testing the electrical and/or thermal properties of theLED devices.

FIGS. 11 to 14 illustrate top views of different embodiments of LEDdevices. Such devices may be similar in many aspects to previouslydescribed LED devices 10 and 50, but can also be useful for a range oflow and/or high voltage applications in addition to attaining differentlight output by pattern variation. For example, FIG. 11 illustrates oneembodiment of an LED device, generally designated 60 which can be usedin lower voltage applications. In one aspect and for example onlywithout limitation, LED device 60 can be operable at approximately 16 V.In one aspect, LED device 60 can be operable at less than approximately16 V, for example, 14 to 16 V. In one aspect, LED device 60 can beoperable at more than approximately 16 V, for example, 16 to 18 V. Inone aspect, using more than 140 LEDs 25, e.g., more than LED device 10and changing the pattern of LEDs 25 can allow LED device 60 to beoperable at lower voltage applications. In one aspect, the pattern canbe changed by electrically connecting less than 14 LEDs 25 together in aseries or string.

FIG. 11 illustrates at least two sets of LEDs arranged in two patternsforming a reticulated array of LEDs 25 within emission area 16. Forexample, a first set of LEDs can comprise second pattern P2, previouslydescribed. A second set of LEDs can comprise a fourth pattern P4. Eachpattern can comprise, for example, 30 strings of five LEDs 25electrically connected in series. That is, fewer than 14 (FIGS. 3A, 3B)LEDs 25 can be electrically connected in series in a given string. Thefirst and last strings of LEDs 25 can comprise five LEDs 25 electricallyconnected in series according to previously described second pattern P2.The second to twenty-ninth strings can comprise another patterndifferent from the first and thirtieth strings. For example, FIG. 11illustrates five LEDs 25 electrically connected in series according topattern P2, the strings can be disposed on conducting pad 30 proximateone or more rounded outer edges of emission area 16. LEDs 25 arranged inthe first and thirtieth strings can, for example and without limitation,be spaced equidistant from each other and uniformly across emission area16 according to pattern P2. LEDs 25 arranged in pattern P2 can comprisea straight line arrangement in which longer axes of LEDs 25 aresubstantially parallel. The shorter axes of LEDs 25 in pattern P2 canalso be at least substantially parallel. Longer axes of LEDs 25 arrangedin pattern P2 can be aligned perpendicular to wirebonds 26. In addition,longer axes of LEDs 25 arranged in pattern P2 can be perpendicular tolonger axes of LEDs 25 arranged in adjacent patterns, e.g., pattern P4.

In one aspect, pattern P4 can comprise five LEDS 25 electricallyconnected in series across conducting pad 30. Pattern P4 can comprise astraight line of LEDs, and each of the five LEDs 25 can be positionedsuch that longer axes of LEDs 25 are substantially aligned along astraight line. In one aspect, longer axes of each LED 25 can be alignedin a same direction as the direction of wirebonds 26 connecting the LEDs25 to conductive traces 33 and 34 disposed below retention material 14.Adjacent strings, e.g., adjacent strings in the second throughtwenty-ninth strings of LEDs 25 connected in pattern P4 can alternateabove and below a straight line such that the LEDs 25 form asubstantially checkerboard type arrangement. That is, a first string ofLEDs 25 arranged in pattern P4 (i.e., the second overall string of LEDs25 disposed below the first string comprising pattern P2) can comprisefive LEDs 25 spaced equidistant apart, leaving a space in betweenadjacent LEDs 25. In the alternative, LEDs 25 in pattern P4 could bewirebonded in a checkerboard arrangement, but that could increase thevoltage at which device 60 is operable. Below the first string of LEDs25 arranged in pattern P4, a subsequent string of LEDs 25 arranged inpattern P4 can be positioned or placed such that the LEDs 25 aresubstantially within and/or slightly below the space between adjacentLEDs 25 of the preceding string. That is, LEDs 25 arranged in pattern P4can comprise a first string aligned such that a bottom edge of each LED25 in the string is aligned along a same first straight line. LEDs 25 ina neighboring subsequent string of pattern P4 can be aligned such that atop edge of each LED 25 is also aligned along the same first straightline as the bottom edge of LEDs 25 in the preceding string. Thus, LEDs25 of preceding and subsequent strings alternate above and/or belowspaces between adjacent LEDs 25 in a given string, and the top andbottom edges of LEDs 25 in adjacent strings can be aligned along a sameline. This arrangement comprises a substantially checkerboard shapedorientation which can advantageously allow LEDs 25 to uniformly emitlight from LED device 60 without one or more adjacent LEDs blockinglight.

Additional strings of LEDs 25 arranged in pattern P4 can alternateaccording to the first two strings just described. Strings of LEDs 25comprising pattern P4 can comprise a same or similar width over emissionarea 16. That is, each adjacent LED 25 of a given string can be spacedapart at equidistant lengths, but the overall string length may not beuniformly across emission area 16. Rather, LEDs 25 can be spaced suchthat the second to twenty-ninth rows form a substantially reticulatedarray over emission area 16. In one aspect, LEDs 25 form a rectangulararray over emission area 16 which utilizes a substantially uniformportion of horizontal segments, or chords of conducting pad 30. In oneaspect, LED device 60 can comprise at least one group of LEDs 25arranged in more than one string of LEDs, where the overallconfiguration can be in a predetermined geometrical shape, such as forexample and without limitation, a rectangle. Any suitable number of LEDs25 may be connected in series. Fewer number of LEDs 25, for example fiveLEDs 25 connected in series as illustrated in FIG. 11 can allow LEDdevice 60 to be suitable for lower voltage applications, for example 16V applications. For illustration purposes, 30 strings of five LEDs 25arranged in one or more patterns are illustrated for operation at lowervoltages, however, any suitable number of strings and/or LEDs 25electrically connected in series is contemplated.

LED device 60 can comprise outermost LEDs 25A electrically connected viaelectrical connectors such as wirebonds 26 to conductive traces 33, 34(FIG. 10). Retention material 14 can then be dispensed at leastpartially about conducting pad 30 and at least partially over wirebonds26. Retention material 14 can be dispensed about emission area 16 whichcan comprise a plurality of LED chips, or LEDs 25 disposed within and/orbelow filling material 40 such as illustrated in FIG. 7. Fillingmaterial 40 can be at least partially contained by retention material14, and retention material can be used to control or adjust variousheights of filling material as may be desirable. Notably, LED device 60can comprise a uniform optical source in the form of single, cohesive,and undivided emission area which can simplify the manufacturing processfor manufacturers of light products requiring a single component. LEDs25 can be spaced a suitable distance apart such that device 60 canadvantageously emit uniform light without having any light blocked byone or more adjacent LEDs 25. The patterns and pattern spacing (i.e.,spacing between adjacent LEDs 25 and spacing between adjacent strings ofLEDs 25) disclosed for example in LED devices 10 and 60 allow foroptimization of light extraction by reducing the amount of light blockedby adjacent LEDs 25 and adjacent strings of LEDs 25. The pattern spacingdisclosed for example in LED devices 10 and 60 can further be configuredand expanded, for example, by increasing the spacing between adjacentLEDs 25 (e.g., to pattern spacing illustrated in FIGS. 12-14B) tomaximum spacing within a given string and between one or more strings tofurther maximize and attain a higher efficiency and light extractionwithin a given LED device.

FIGS. 12 to 14B illustrate top views of LED devices which can beoperable at higher voltages such as, for example only and not limited toapproximately 42 V. In one aspect, LED devices illustrated by FIGS. 12to 14B can comprise more than five LEDs 25 per string such that thedevice is configured to operate at greater than approximately 16 V. FIG.12 illustrates an LED device generally designated 70 having, forexample, five strings of 14 LEDs 25. LED device 70 can comprise stringsof LEDs 25 arranged in one or more different patterns. For example, thefirst and last strings proximate rounded edges of conducting pad 30 cancomprise 14 LEDs 25 arranged in previously described pattern P2. Thelongitudinal axes of adjacent LEDs 25 in pattern P2 can be aligned suchthat they are at least substantially parallel. The longitudinal axes ofadjacent LEDs 25 in pattern P2 can be at least substantiallyperpendicular to the direction of wirebonds 26 connecting adjacent LEDs25. For each LED device described, any shape, orientation, or structureof LEDs is contemplated. In one aspect, LED device 70 can comprise 70total LEDs 25.

Still referring to FIG. 12, strings of LEDs 25 disposed betweenoutermost strings of second pattern P2 can comprise a different pattern,for example, third pattern P3 previously described in FIGS. 3A and 3B.Third pattern P3 can comprise a substantially checkerboard pattern orarrangement of LEDs 25 electrically connected in series. In one aspect,pattern P3 can be disposed between and/or alternate with strings of LEDshaving second pattern P2. The checkerboard pattern or third pattern P3can comprise a set of LEDs 25 alternating both above and below ahorizontal line. LED device 70 can be disposed uniformly across emissionarea 16 and/or conducting pad 30, for example. In general, adjacent LEDs25 in each of the strings of LED device 70 can be spaced at equidistantintervals to utilize a substantial portion of horizontal segments ofconducting pad 30. That is, LEDs 25 in device 70 can occupy a greateramount of surface area and length of horizontal segments of conductingpad 30 than previously described LED device 60. For illustrationpurposes, five strings of 14 LEDs 25 arranged in two different patternsare illustrated, however, any suitable number of strings and/or LEDs 25electrically connected in series is contemplated.

FIGS. 13A and 13B illustrate further embodiments of LED devices. In oneaspect, LED devices in FIGS. 13A and 13B comprise six strings of 14 LEDs25, for a total of 84 LEDs 25. Referring to FIG. 13A, LED device,generally designated 80 can comprise one or more strings of LEDs 25arranged for example in a single pattern across conducting pad 30. Theone or more strings of device 80 can have the same and/or differentpatterns. For illustration purposes, previously described pattern P3 isillustrated. LEDs 25 can be arranged in a checkerboard patternalternating above and below a horizontal line. Adjacent LEDs 25 can bespaced a substantially uniform distance from each other across a largeportion of the surface area of conducting pad 30. Checkerboardarrangements, e.g., pattern P3 can advantageously allow the LEDs 25 touniformly emit light from LED device 80 without one or more adjacentLEDs 25 blocking light.

FIG. 13B illustrates another embodiment of a six string LED device,generally designated 85. Like LED device 80, LED device 85 can comprisesix strings of 14 LEDS 25. Spacing between adjacent LEDs 25 within thesame string and adjacent LEDs 25 within different strings has beenmaximized to minimize the amount of light absorbed by adjacent LEDs. Inone aspect, LED device 85 comprises previously illustrated first patternP1 (FIG. 3A) as the first and last strings. Notably, LEDs 25 of patternsP1 and P3 extend at least substantially the full length and width ofconducting pad 30. The second through fifth strings of LEDs 25 withinLED device 85 comprise pattern P3. When comparing the six stringarrangement of FIG. 13A to the six string arrangement of FIG. 13B, it isapparent that the strings of FIG. 13B are more spread out, i.e.,vertically and horizontally spaced further apart on conducting pad 30 toutilize more of the mounting area. Maximizing the space between stringsof LEDs 25 can minimize the amount of light absorbed or blocked byneighboring LEDs 25.

In one aspect, inter-string spacing, that is, spacing between adjacentLEDs 25 of the same string has been increased by at least approximately31%, or by 125 μm, or greater in the vertical direction for pattern P3from LED device 80 to LED device 85. Similarly, inter-string spacing ofLEDs 25 in pattern P1 has been increased and/or optimized in both thehorizontal and vertical directions. For example, spacing has beenincreased approximately 41%, or by 225 μm, or greater, in the horizontaldirection and by at least approximately 27%, or by 210 μm, or greater inthe vertical direction from P1 in LED device 10 to P1 in LED device 85.Intra-string spacing i.e., spacing between LEDs 25 of adjacent stringscan be increased by at least approximately 68%, or by 750 μm, or greaterin LED device 85. Notably, although LED device 85 can comprise the samenumber of LEDs 25 as LED device 80, e.g., 84 LEDs, LED device 85 cancomprise at least approximately a 1% to 3%, or greater, increase inefficiency and brightness when compared to LED device 80. In one aspect,increasing the spacing between adjacent LEDs 25 as described canincrease the efficiency by at least approximately 2.5% or greater fromone six string arrangement to another, e.g., LED device 85 can comprisea 2.5% or greater increase in efficiency over LED device 80. Forexample, LED device 85 can have a light output of at least approximately2.5% or higher than the light output of LED device 80 described above,which can comprise approximately 1050 lumens or more at 11 watts, orapproximately 2000 lumens or more at 27 watts.

FIGS. 14A and 14B illustrate further embodiments of LED devices. In oneaspect, the LED devices in FIGS. 14A and 14B comprise eight strings of14 LEDs 25. Referring to FIG. 14A, an LED device generally designated 90is illustrated, and can be operable at higher voltages, not limited togreater than or equal to approximately 42 V. LED device 90 can compriseone or more strings of LEDs 25 arranged in one or more patterns acrossemission area 16 and/or conducting pad 30. In one aspect, LED device 90can comprise eight strings of LEDs 25 arranged in more than one pattern.Each string of LEDs 25 can comprise 14 LEDs 25, or 112 total LEDs. Inone aspect, the first and last strings can comprise previously describedpattern P2. The second through seventh strings of LEDs 25 can comprisepreviously described pattern P3. Notably, LED devices illustrated byFIGS. 11 to 14B can comprise a uniform optical source in the form ofsingle, cohesive, and undivided emission area which can simplify themanufacturing process for manufacturers of light products requiring asingle component.

FIG. 14B illustrates another embodiment of an eight string LED device,generally designated 95. Like LED device 90, LED device 95 can compriseeight strings of 14 LEDS 25. Spacing between adjacent LEDs 25 within thesame string and adjacent LEDs 25 within different strings has beenmaximized to minimize the amount of light absorbed by adjacent LEDs. Inone aspect, LED device 95 can comprise previously illustrated firstpattern P1 (FIG. 3A) as the first and last strings. The second andseventh strings can comprise pattern P2, and the third through sixthstrings can comprise pattern P3. Notably, LEDs 25 of patterns P1, P2,and P3 extend at least substantially the full length and width ofconducting pad 30. LEDs 25 of P1, P2, and P3 can be spaced further aparthorizontally and/or vertically such that an amount of light blocked byadjacent LEDs 25 can be decreased. In one aspect, pattern P1 spacing hasbeen increased at least approximately 41%, or by 225 μm, or greater inthe horizontal direction and by at least approximately 27%, or by 210μm, or greater in the vertical direction from P1 in LED device 10 to P1in LED device 95. Similarly, horizontal and/or vertical spacing betweenLEDs 25 in pattern P2 can be increased at least approximately 4% orgreater over P2 in LED device 90. Intra-string spacing i.e., spacingbetween LEDs 25 of adjacent strings can be increased by at leastapproximately 68%, or by 750 μm, or greater in LED device 95. Notably,although LED device 95 can comprise the same number of LEDs 25 as LEDdevice 90, e.g., 112 LEDs, LED device 95 can have at least anapproximate 1% to 2%, or greater, increase in efficiency and brightnesswhen compared to LED device 90.

In one aspect, LED devices 10, 60, 70, 80, and 90 disclosed by FIGS. 3A,3B, and 11 to 14B can comprise a large quantity of LEDs 25 arranged inone or more patterns over conducting pad 30. In one aspect, LED devicesdisclosed herein comprise a quantity of more than 64 LEDs 25. Forexample, in one aspect and without limitation, LED device 10 cancomprise 140 total LEDs, or 10 strings of LEDs 25 electrically connectedin series. LED device 60 can comprise 150 total LEDs, or 30 strings offive LEDs 25 electrically connected in series. LED device 70 cancomprise 70 total LEDs, or five strings of 14 LEDs 25. LED device 80 cancomprise 84 total LEDs, or six strings of 14 LEDs 25. LED device 90 cancomprise 112 total LEDs, or eight strings of 14 LEDs 25. LEDs 25 used inLED devices described herein can comprise a small footprint, or surfacearea when compared to conducting pad 30. For example and withoutlimitation, LEDs 25 can comprise chips of the following dimensions inTable 1 below:

TABLE 1 Length (μm) Width (μm) LED chip size 350 470 230 660 500 500 520700

In one aspect and without limitation, conducting pad 30 can comprise aradius of approximately 6.568 mm and an area of approximately 135.7 mm².Thus, the ratio of the area of a single LED chip 25 and the area ofconducting pad 30 can comprise approximately 0.0027 or less. In oneaspect, the ratio of the area of a single LED chip 25 and the area ofconducting pad 30 can comprise approximately 0.0018 or less. In otheraspects, the ratio can comprise approximately 0.0012 or less. Table 2below lists various LED 25 chip sizes and the area of conducting pad 30.LEDs 25 can comprise chips that are small compared to the area ofconducting pad, that is, approximately 0.0027 of the area of theconducting pad or less. Any chip size may be used however.

TABLE 2 Ratio of Chip Area to Conducting Pad Conducting Pad Chip Size(μm) Area (mm) Area 350 × 470 135.7098 0.0012 230 × 660 135.7098 0.0011500 × 500 135.7098 0.0018 520 × 700 135.7098 0.0027

Using a large quantity of LEDs 25 comprising a smaller footprint over asingle emission area can advantageously allow for more uniform lightoutput in addition to desirable optical properties such as highbrightness as the LEDs 25 can be arranged into one or more uniformpatterns over a portion of emission area 16. The concentrated patternsof LEDs 25 can allow for concentrated light emission. In one aspect, thedensity or spacing of LEDs 25 in the one or more patterns describedherein can be adjusted such that light will not be absorbed or blockedby adjacent LEDs 25. That is, patterns and arrangements of LEDs 25disclosed herein may improve light extraction by minimizing the amountof light absorbed by adjacent, or neighboring LEDs 25. The number ofLEDs 25 per string can allow LED devices to be operable at low to highvoltages. For illustration purposes, four patterns have beenillustrated. However, any suitable pattern of LEDs 25 is contemplated.Each string of LEDs 25 can comprise a single pattern or a combination ofmore than one pattern.

FIGS. 15A and 15B illustrate methods of die attach that can, for exampleand without limitation, be used for LED devices according to thedisclosure herein. LED 25 can comprise a backside metal pad or bondinglayer 100 for mounting over conducting pad 30. Bonding layer 100 cancomprise a length of the entire bottom surface LED 25 or a portionthereof. For illustration purposes, bonding layer 100 is illustrated ashaving a same length as the entire bottom surface of LED 25, however,any configuration is contemplated. LED 25 can comprise lateral sides 104which can extend between an upper surface and the bottom surface of LED25. FIGS. 15A and 15B illustrate inclined lateral sides 104, however,lateral sides 104 can be substantially vertical or straight where astraight-cut LED is selected. FIGS. 15A and 15B illustrate LEDs 25having an upper surface of a greater surface area than an area of bottomsurface comprising bonding layer 100. However, upper surface can be of asmaller surface area than the surface area of bonding surface. LEDs 25can comprise a square, rectangle, or any suitable shape in addition tohaving any suitable lateral side configuration.

Any suitable die attach method can be used to mount LED 25 overconducting pad 30 in any of the LED devices previously described. In oneaspect, any suitable optimized die attach method and/or materials can beused. For example, optimized die attach methods can comprisemetal-to-metal die attach methods for facilitating attachment of one ormore metals on and/or between LED 25 and conducting pad 30. FIG. 15Aillustrates an example of a metal-to-metal die attach method which canbe eutectic or non-eutectic. This metal-to-metal die attach method cancomprise using an assist material 106 to facilitate the metal-to-metaldie attach. In one aspect, a flux-assisted eutectic metal-to-metal dieattach method can be used and in other aspects a metal-assistednon-eutectic metal-to-metal die attach method can be used. In aflux-assisted eutectic, or flux eutectic, die attach method, bondinglayer 100 can comprise a metal alloy having a eutectic temperature, forexample, but not limited to, an alloy of gold (Au) and tin (Sn). Forexample, bonding layer 100 can comprise an 80/20 Au/Sn alloy having aeutectic temperature of approximately 280° C. In the flux eutectictechnique, assist material 106 can comprise a flux material. In thenon-eutectic technique, assist material 106 can comprise a metallicmaterial. The assist material 106 can comprise a conduit forfacilitating the metal-to-metal die attach between the bonding layer 100and conducting pad 30 when the bonding layer 100 is heated above theeutectic temperature. The metal of bonding layer 100 can flow into andattach to the metal of conducting pad 30. The metal of bonding layer 100or can atomically diffuse and bond with atoms of the underlying mountingconducting pad 30. In one aspect, flux used in a flux-assisted eutecticmethod can comprise a composition, for example, 55-65% rosin and 25-35%polyglycol ether in addition to small amounts of other components. Anysuitable flux material can be used however.

Flux-assisted eutectic die attach methods can be tedious, and it isunexpected to use such methods when attaching a large quantity of LEDs25 in predetermined arrangements and/or an array. Flux eutectic dieattach according to the present subject matter can comprise dispensingflux assist material 106, that can be liquid at room temperature, in anamount to be precisely the right volume to avoid either swimming of theLEDs 25 or poor die attach if too much or too little flux is used.Flux-assisted eutectic die attach according to the present subjectmatter can also require the right composition for each of the fluxassist material 106 and bonding metal 100 of the emitter chips.Flux-assisted eutectic die attach according to the present subjectmatter can optimally utilize a very clean and flat surface andsubstrates that do not move or bend during heating and cooling such tostress the solder joint. Flux-assisted eutectic according to the presentsubject matter can utilize a fine surface roughness that is small enoughnot to encumber the Au/Sn bonding surface of the emitter chips whilebeing rough enough to allow flux to escape during heating. The heatingprofile can be matched perfectly to the bonding metal 100, such as Au orAuSn, to ensure a good weld between the bonding metal 100 and underlyingconducting pad 30. Using flux-assisted eutectic for die attach accordingto the present subject matter also can utilize an inert atmosphere, suchas a nitrogen atmosphere, to reduce oxygen gas (O₂) levels and alsoallow gravity to apply a downward force on LEDs 25. This can reduce theamount of oxidation at the metal-to-metal bond between bonding layer 100and underlying conducting pad 30.

Still referring to FIG. 15A, a non-eutectic metal-to-metal die attachmethod can be used which can also comprise an assist material 106,wherein the assist material 106 can comprise a metallic material. Inthis aspect, bonding layer 100 can comprise a single metal or a metalalloy. For example, bonding layer 100 can comprise Au, Sn, or AuSn. Innon-eutectic methods, the bonding layer does not need to reach or exceeda temperature, for example, a eutectic temperature. In this aspect,assist material 106 can comprise a metallic material to facilitate themetal-to-metal bonding. For example, assist material 106 can compriseAuSn paste or Ag epoxy. Any suitable metallic assist material 106 can beused. The metal of bonding layer 100 can attach to the metal of theassist material 106. The metal of the assist material 106 can alsoattach to the metal of conducting pad 30. In one aspect, a metal“sandwich” forms between bonding layer 100, assist material 106, andconducting pad 30 in non-eutectic metal-to-metal attach techniques wherea metallic assist material 106 is used. Metal-assisted, non-eutectic dieattach can be tedious, just as flux-assisted methods, and it is alsounexpected to use such methods when attaching LEDs 25 within one or morepatterns for LED devices described herein. Metal-to-metal attachmentusing an assist material 106 can be hard to control and tedious whenattaching multiple small footprint LEDs within a device.

FIG. 15B illustrates a metal-to-metal die attach technique which doesnot require an assist material 106. One such method can comprise athermal compression die attach method wherein the metal of bonding layer100 will directly attach to the metal of conducting pad 30. The thermalcompression method can be eutectic or non-eutectic. In one aspect,thermal compression can be used when bonding layer 100 comprises analloy having a eutectic temperature. In other aspects, bonding layer 100can comprise a metal not having a eutectic temperature. Conducting pad30 can comprise any suitable metal, not limited to a Cu, Al, Ag, or Ptlayer within a metal core printed circuit board (MCPCB). Bonding layer100 comprises any suitable metal. In one aspect, bonding layer 100 cancomprise a layer of Sn having any suitable thickness. In one aspect,bonding layer 100 can comprise a thickness greater than approximately 0μm. In one aspect, bonding layer 100 can comprise a bonding layer equalto or greater than at least approximately 0.5 μm. In one aspect, bondinglayer 100 can comprise a layer of Sn having a thickness of at leastequal to or greater than approximately 2.0 μm. Unlike the flux-assistedeutectic or metal-assisted non-eutectic methods just described, thermalcompression metal-to-metal die attach techniques can utilize an externaldownward force F as illustrated in FIG. 15B.

Force F can comprise a compression delivered in a heated environment,thus deemed a thermal compression, as opposed to dispensing a flux ormetallic assist material 106. The thermal compression technique is analternative die attach method developed to reduce metal squeeze outalong the conducting pad 30 which can form Shottky or Shunt defects andallow subsequent leakage of current and other various and relatedproblems. In one aspect, the bonding temperature in thermal compressiontechniques can be approximately 255-265° C. after optionally subjectingconducting pad 30 to a pre-heat treatment or process. Conducting pad 30can be heated to a mounting temperature of at least 20° C. above themelting temperature of the bonding layer 100. The bonding time can beapproximately 300 msec and the bonding force can be approximately50+/−10 grams (g). Predetermined settings can be important for thismethod, including adequate preheat, bonding temperature, bonding time,and bonding force. The equipment and predetermined settings for use withthermal compression methods can be difficult to use and/or maintain, andit is unexpected to use such methods when attaching a large quantity ofLEDs 25 in an array and/or one or more patterns. Metal-to-metal methodsfor attaching an array of LEDs in LED devices is not known and isunexpected to use flux-assisted eutectic, metal-assisted non-eutectic,or thermal compression die attach techniques for attaching one or morestrings of LEDs 25 in an array or pattern arrangement.

Embodiments of the present disclosure shown in the drawings anddescribed above are exemplary of numerous embodiments that can be madewithin the scope of the appended claims. It is contemplated that theconfigurations of LED devices and methods of making the same cancomprise numerous configurations other than those specificallydisclosed.

What is claimed is:
 1. A light emitting diode (LED) device, comprising:a substrate; a plurality of LED chips disposed in an array over thesubstrate for emitting light from a light emission area, wherein the LEDchips are spaced apart to extend at least substantially a full length ofthe light emission area and at least substantially a full width of thelight emission area to minimize light absorbed or blocked by neighboringLED chips, and wherein at least some of LED chips in the array areserially connected in a checkerboard pattern with LED chips alternatingboth above and below a horizontal line; and a retention material atleast partially disposed about the plurality of LED chips.
 2. The deviceof claim 1, wherein each LED chip comprises a length of approximately470 μm or less and a width of approximately 350 μm or less.
 3. Thedevice of claim 2, wherein the array of LED chips comprises: at least afirst string of LED chips; and at least a second string of LED chips,wherein an intra-string spacing between one LED chip in the first stringand a closest LED chip in the second string is more than twice the widthof the LED chips.
 4. The device of claim 3, wherein the intra-stringspacing is approximately 750 μm or more.
 5. The device of claim 1,wherein the array comprises multiple strings of serially connected LEDchips, and wherein an intra-string spacing between one LED chip in thefirst string and a closest LED chip in the second string isapproximately 750 μm or more.
 6. The device of claim 1, wherein thearray of LED chips comprises at least a first string of seriallyconnected LED chips, and wherein an inter-string spacing betweenadjacent at least two LED chips in the first string is approximately 125μm or more.
 7. The device of claim 6, wherein the inter-string spacingis approximately 210 μm or more.
 8. The device of claim 6, wherein theinter-string spacing is approximately 225 μm or more.
 9. The device ofclaim 1, wherein the array of LED chips comprises at least four stringsof serially connected LED chips.
 10. The device of claim 1, wherein thearray of LED chips comprises at least six strings of serially connectedLED chips.
 11. The device of claim 1, wherein the array of LED chipscomprises at least eight strings of serially connected LED chips. 12.The device of claim 1, wherein the array comprises multiple strings ofserially connected LED chips arranged in more than one pattern.
 13. Thedevice of claim 12, wherein at least one pattern is linear.
 14. Thedevice of claim 12, wherein at least one pattern is non-linear.
 15. Thedevice of claim 1, wherein the LED chips are directly attached to amounting pad.
 16. The device of claim 15, wherein the LED chips aredirectly attached to the mounting pad via flux-assisted eutectic,metal-assisted non-eutectic, or thermal compression die attachtechnique.
 17. The device of claim 1, wherein each of the plurality ofLED chips are adapted to emit a same color of light.
 18. The device ofclaim 1, wherein the plurality of LED chips are adapted to emit at leasttwo different colors of light.
 19. A method of providing a lightemitting diode (LED) device, the method comprising: providing asubstrate; serially connecting a plurality of LED chips in an array overthe substrate for emitting light from a light emission area, wherein theLED chips extend at least substantially a full length of the lightemission area and at least substantially a full width of the lightemission area whereby light absorbed or blocked by neighboring LED chipsis minimized, and wherein at least some of serially connected LED chipsin the array are disposed in a checkerboard pattern with LED chipsalternating both above and below a horizontal line; and dispensing aretention material at least partially about the light emission area. 20.The method of claim 19, wherein each LED chip comprises a length ofapproximately 470 μm or less and a width of approximately 350 μm orless.
 21. The method of claim 20, wherein serially connecting aplurality of LED chips comprises: serially connecting LED chips in afirst string of LED chips; serially connecting LED chips in a secondstring; and wherein an intra-string spacing between one LED chip in thefirst string and a closest LED chip in the second string is more thantwice the width of the LED chips.
 22. The method of claim 21, whereinthe intra-string spacing is approximately 750 μm or more.
 23. The methodof claim 19, wherein the array comprises multiple strings of seriallyconnected LED chips, and wherein an intra-string spacing between the oneLED chip in the first string and the closest LED chip in the secondstring is approximately 750 μm or more.
 24. The method of claim 19,wherein serially connecting a plurality of LED chips in an arraycomprises serially connecting LED chips in a first string across thelength of the mounting pad, and wherein an inter-string spacing betweenat least two adjacent LED chips within the first string is approximately125 μm or more.
 25. The method of claim 24, wherein the inter-stringspacing is approximately 210 μm or more.
 26. The method of claim 24,wherein the inter-string spacing is approximately 225 μm or more. 27.The method of claim 19, wherein serially connecting a plurality of LEDchips comprises serially connecting at least four strings of LED chips.28. The method of claim 19, wherein serially connecting a plurality ofLED chips comprises serially connecting at least six strings of LEDchips.
 29. The method of claim 19, wherein serially connecting aplurality of LED chips comprises serially connecting at least eightstrings of LED chips.
 30. The method of claim 19, wherein seriallyconnecting a plurality of LED chips comprises arranging the LED chips inmore than one pattern.
 31. The method of claim 30, wherein at least onepattern is linear.
 32. The method of claim 30, wherein at least onepattern is non-linear.
 33. The method of claim 19, further comprisingdirectly attaching the LED chips to a mounting pad.
 34. The method ofclaim 31, wherein directly attaching the LED chips comprises attachingthe LED chips via a flux-assisted eutectic, a metal-assistednon-eutectic, or thermal compression die attach technique.